1. Field of the Invention
The present invention relates to a photogravure press used for manufacturing a multilayer-ceramic electronic component and a method for manufacturing a multilayer-ceramic electronic component, conducted by using the photogravure press, and in particular, the present invention relates to a technique for improving smoothness of a paste film formed by gravure printing.
2. Description of the Related Art
In order to manufacture a multilayer-ceramic electronic component such as a multilayer ceramic capacitor, for example, a step of forming a conductive paste film functioning as an internal electrode on a ceramic green sheet is executed. The internal electrode defined by the conductive paste film is required to have high patterning accuracy. As a technique for satisfying the above requirement, gravure printing has attracted attention (for example, see Japanese Unexamined Patent Application Publication No. 9-76459 (hereinafter, referred to as Patent Document 1)).
Patent Document 1 discloses an apparatus for manufacturing an electronic component, in which, in order to make uniform the thickness of the peripheral portion of the paste film formed by gravure printing, of a plurality of cells formed in each of image areas which have print paste applied thereon and which are formed on the circumference surface of a gravure roll, a portion of the cells lying in the peripheral portion of the image area are formed so as to have open areas that are smaller than those of another portion of the cells lying in the central portion of the image area, and the depths of the cells lying in the peripheral portion are made smaller than those of the cells lying in the central portion.
Unfortunately, in the apparatus disclosed in Patent Document 1, since the cells formed in the image area are independent from each other, the ratio of the area of the cells with respect to the overall area of the image area is relatively small, and also, since print paste between the adjacent cells is unlikely to flow during printing, the apparatus is not suitable for forming a paste film especially having a relatively large area and often causes unevenness of printing.
As a technique for solving the above-described problems, for example, Japanese Examined Utility Model Registration Application Publication No. 5-41015 (hereinafter, referred to as Patent Document 2) has proposed a photogravure plate, although not intended to be applied to electronic components, in which walls defining a plurality of cells in an image area are arranged so as to extend at an angle with the printing direction and have cuts so as to allow the adjacent cells to communicate with each other.
According to the technique set forth in Patent Document 2, the ratio of the area of a region (that is, the cells and the cuts) in which the print paste can be held can be increased with respect to the overall area of the image area, and also, it can be expected that the print paste flows through the cuts.
Unfortunately, according to the technique set forth in Patent Document 2, since the gap of each cut is formed smaller than the width of each wall, when print paste, such as conductive paste, having a relatively high viscosity is used, the print paste is limited to flow between the adjacent cells, thereby sometimes causing a printed paste film to have a trace of the cell or forming a rough paste film.
Also, according to the technique set forth in Patent Document 2, since the walls defining the plurality of cells formed in the image area are arranged so as to extend at an angle with the printing direction, so-called stringiness of the print paste occurs at an angle with the circumferential surface of the gravure roll when a substrate sheet is detached from the gravure roll, whereby local irregularities are likely to occur in the peripheral portion of the printed paste film. Inconstancy in the direction of the stringiness causes reciprocal overlapping, which leads further to variation in the thickness of paste films.